When an electromagnetic wave having a short wavelength of several tens of nanometers or less is dealt with, a difference in refractive index for any such electromagnetic wave between different materials is extremely small, specifically, 10−4 or less, and thus, for example, a total reflection angle becomes extremely smaller. For controlling such electromagnetic wave including an X-ray, a large-scale spatial optical system is usually used. As main parts of which the spatial optical system is formed, there is given a multilayer mirror obtained by alternately laminating materials having different refractive indices, and this multilayer mirror is playing various roles such as beam shaping, spot size conversion, and wavelength selection.
A conventional X-ray waveguide such as a polycapillary propagates, in contrast to such mainstream spatial optical system, an X-ray by confining the X-ray in itself. Researches have been recently conducted on—ray waveguides, which propagate X-ray by confining the X-ray in a thin film or a multilayer film with a view to reducing the size, and improving the performance, of optical systems.
Specifically, researches have been conducted on, for example, multiple thin-film X-ray waveguides each formed so that an X-ray is confined by total reflection in each waveguide's core.(see NPL 1), and a thin-film waveguide of such a shape that a waveguiding layer is interposed between two layers of one-dimensional periodic structures (see NPL 2).